[Effects of magnesium, manganese and cobalt ions on the activity of Ca2+-dependent ATPase of skeletal muscle plasma membranes].

Bivalent cations (Mn and Co) are found to activate ATPase activity of sarcolemma in the same degree, as Mg and Ca. The increase of the activity of Ca2+-dependent ATPase under the certain conditions of treatment of sarcolemma with KCl-Triton X-100 solution is not accompanied by the increase of ATPase activity in the presence of Mn and Co ions. ATPase activities in the presence of these ions correlate with the activity of Mg2+-dependent ATPase. Bivalent cations Mg, Mn and Co are competitive inhibitors for Ca2+-dependent ATPase. The apparent inhibition constants are determined to be 3,5-10(-5) M for Mg, 0,7-10(-3) M for Co and 1,5-10(-3) M for Mn. It is supposed that Ca2+-dependent ATPase has similar selectivity to bivalent cations as calcium influx that follows depolartization of plasma membrane.